Propeller fans blowing air in an axial direction have been used in various technical fields. Moreover, providing a static blade straightening an airflow blown by the propeller fan for a fan housing, which houses such a propeller fan, is known in the art. For example, Cited Reference 1 discloses a fan unit including a propeller fan and a diffuser, which converts kinetic energy of air blown out of the propeller fan into pressure energy. Note that this diffuser includes an exterior and an interior shroud, each having a cylindrical shape, and a plurality of static blades installed between the exterior and interior shrouds.